1. Field of the Invention
The present disclosure generally relates to devices that are used in nerve stimulation. More particularly, the present disclosure relates to an overwrap for wrapping nerve stimulation electrodes, such as are used in vagus nerve stimulation.
2. Description of the Related Art
Since its introduction, nerve stimulation has been used to treat a variety of neurological conditions. Vagus Nerve Stimulation (VNS) is one type of nerve stimulation that has been used as a treatment for intractable epilepsy. Typically, this involves stimulating the left cervical vagus nerve via an implanted electrode (the vagus nerve can also be stimulated outside of the cervical area and on the right vagus). VNS has been available for clinical treatment of epilepsy in the U.S. since 1997. The therapy is achieved through an implanted pulse generator that delivers a bipolar, biphasic pulse. The implant procedure is very similar to the implantation of a pacemaker. The generator is implanted subcutaneously, typically in the upper left chest wall. An electric lead is connected between the pulse generator and the electrode using a subcutaneous tunneling tool to the vagus nerve, which lies in the carotid sheath.
Several types of nerve stimulation electrodes have been developed. These include the nerve cuff (a cylinder with an open side), which is placed around the nerve and sutured closed, and helical electrodes, which can be flexible and provide a “self-sizing” feature due to their shape. Nerve stimulation electrodes are often attached in groups. That is, two or three electrodes are attached along the nerve, and are connected to the pulse generation device via an electric lead or wire. One of the devices attached to the nerve can be an electrically inactive electrode-type device, which serves as a tether or anchor for the group of electrodes. The electric lead can be attached to this tether electrode first, thus preventing tension or stress on the lead from being transmitted to the electrically active electrodes.
Some VNS electrodes can be difficult and time consuming to attach to a nerve. Where a surgeon applies three electrode devices (two electrodes and one tether) to the nerve, each of the three elements may need to be laced around the nerve independently. Additionally, ingrowth of tissue around and between electrodes can affect their effectiveness and can significantly hinder surgical removal or other adjustment of electrodes after implantation.
It is also desirable for electrodes to provide effective nerve stimulation with minimum power consumption. However, some of the current that is applied to nerve stimulation electrodes passes into surrounding tissue, rather than being directed into the nerve.
It is believed that some nerve stimulation electrodes and electrode systems that are currently available fall short in these areas. The present disclosure is directed to overcoming, or at least reducing the effects, of one or more of the issues set forth above.